The present invention relates to a sachet or small bag adapted for accommodating a gas-evolving pest control agent.
Solid pest control agents are known which when exposed to humid air will slowly release gaseous active substances. Such pest control agents may comprise hydrolyzable alkaline earth and/or earth metal phosphides, e.g. calcium phosphide, magnesium phosphide or aluminium phosphide, preferably aluminium phosphide, which are caused to release phosphine gas due to the moisture contained in the atmosphere or in a commodity to be fumigated. Such pest control agents are employed for example for the control of pests in stores or silos for grain, tobacco or other agricultural commodities, foodstuffs and luxury commodities. The pest control agent thus serves to eradicate animal organisms, for example bugs, beetles, moths, roaches or other insects or worms and even rodents such as mice and rats. In this context it is known to enclose such pest control agents into paper sachets which in use are introduced into the stored commodities. The pest control agent will then decompose slowly n the paper sachet and release its pest eradicating gaseous decomposition products through the walls of the sachet. The dust-like residues of the pest control agent on the other hand are to be retained by the paper sachet. The paper used for this purpose has to comply with special requirements regarding strength, gas permeability and water repellent properties.
However, such paper can be processed only within limits by automatic equipment (such as for example edge-sealing bag-forming machines, tubular bag-forming machines etc.) In general they are closed by sewing which is a labour-intensive operation. It may also happen that the sewing seams come loose and the poisonous contents then enter into the commodities to be treated.
A sachet for the accommodation of phosphine-evolving pest control agents is known also, composed of a gas pervious non-woven fabric of which the mesh openings are of predetermined dimensions. Materials mentioned for such non-woven fabrics include those based on cellulose or certain synthetic polymers. It is also stated that the manufacture of the sachets may proceed from a continuous length of non-woven fabric, inter alia by welding with the application of heat and/or ultrasonics. The aforegoing offers the advantage that the manufacture of a welded seam is less labor-intensive than the interconnecting of the layers of non-woven material or the various sides of such materials by adhesive action or sewing.
However, it was found that there is a need for improvement with regard to the welding and sealing properties of the non-woven fabrics used for the known sachets. In practice this applies both to the formation of a welding seam as such, as well as with regard to its strength and reliability when the sachets filled with pest control agent are used.
There accordingly exists a need for the provision of a sachet made of a material which on the one hand provides the gas permeability required in use, but which nevertheless retains the dust-like residues of the decomposed pest control agent, in addition to being very durable in character and being very suitable for being processed into a sachet of the desired properties by welding or sealing with heat and/or ultrasonics, preferably with heat.
To this end the present invention teaches inter alia that the sachet may be manufactured in a manner known per se from a special or specially selected non-woven fabric.